PORTLAND AERIAL PORTLAND, OREGON

Body Panel Dislocation Incident Incident Date: December 4 th , 2018 Investigation Dates: December 11 th & 12 th , 2018

Portland Tram Incident Report

Project Information

Project:

Prepared for: City of Portland Richard Eisenhauer, Program Manager Bureau of Transportation 1120 S.W. 5 th Ave. Portland, OR 92704 [email protected]

Reviewing Agency

Jurisdiction : City of Portland

Project Representative

Prepared by : Ridgeline Engineering Company 1600 Washington Ave. #2 Golden, CO 80401 303.482.3186 rdgline.com

Contact : Joel Deis , P.E. (303) 482-3186

Project Reference: #006.00 6

Revisions: 1. 10 January 2019 – Revised narrative in sections 4 & 5 to reflect current design methodology. Changed image in figure 10 to show new and old tether components. 2. 15 April 2019 – Updated several photos, changed narrative in multiple sections.

Ridgeline Engineering Company April 2019

Portland Aerial Tram Body Panel Dislocation Incident

The technical material and data contained in this document were prepared under the supervision and direction of the undersigned, whose seal, as a professional engineer licensed to practice as such, is affixed below.

04/15/2019

Expires: 12/31/19

Prepared by Joel Deis , P.E.

SCOPE OF INSPECTION

The word inspection in this report refers to a visual inspection of the as-built condition of the tramway at the time of our site visit. Evaluation of the existing structure requires that certain assumptions be made regarding conditions existing at the time of the described failure. Elements that could not be observed are excluded from this report. Therefore, this report reflects the findings of our inspection after the described failure and our professional analysis of that failure, but is not intended to be a definitive and certain explanation of the causes of the failure nor a guaranty that such a failure will not occur in the future.

Our inspection was performed in a manner consistent with the degree of care and skill ordinarily exercised by members of the same profession currently practicing under similar circumstances. Ridgeline makes no warranty, certification, or guarantee, express or implied, as to its professional services rendered in the creation of this report.

Ridgeline Engineering Company April 2019

Portland Aerial Tram Body Panel Dislocation Incident

TABLE OF CONTENTS

1. Introduction ...... 2

2. Description of System ...... 2

3. Analysis of Failure ...... 5

4. Document Review and Maintenance Procedures ...... 8

5. Remediation ...... 8

6. Interim Operations ...... 9

7. Conclusion ...... 9

LIST OF APPENDICES

Appendix A – Observation Photos Appendix B – Doppelmayr Incident Report

Ridgeline Engineering Company 1 January 2019 Portland Aerial Tram Body Panel Dislocation Incident

1. INTRODUCTION

On December 4 th , 2018 at 11:52 AM the uphill roof panel from Cabin #2 of the Portland Aerial Tramway fell during a trip. The panel landed on the staircase of the bridge located below and struck a pedestrian. The pedestrian was treated for minor injuries at the scene and refused additional medical care. The purpose of this report is to document the circumstances that led up to this event and what measures should be taken to prevent a situation like this from occurring again in the future.

2. DESCRIPTION OF SYSTEM

The Portland Aerial Tramway first went into service in December of 2006 to assist the transportation of staff, patients and visitors of Oregon Health Sciences University (OHSU). Additionally, the system was designed to move the general public and is owned by the Portland Bureau of Transportation (PBOT). This system is unique in that it was constructed not only to be an integral part of the City’s transportation system, it is also a landmark with several architectural features designed to improve the aesthetics of the system. One of these features is the overall shape of the cabins. Typically, aerial tramway cabins have a rectangular profile rather than the curved shape of the cabins in this system. Examples of two different cabins can be seen below:

Figure 1 – Portland Tram Cabin (Left); “Typical” Rectangular Tram Cabin (Right)

Ridgeline Engineering Company 2 April 2019 Portland Aerial Tram Body Panel Dislocation Incident

The cabins for the Portland Aerial Tram were designed and manufactured by Gangloff Cabins in Switzerland. Their construction is unique in that they are essentially a rectangular cabin, similar to a more typical installation, with decorative paneling wrapped around to give them their unique shape. Figure 2 & Figure 3 below show a cabin in service and what the top looks like with the paneling removed.

Figure 2 – Portland Tram Cabin

Figure 3 – Tram Cabin from Above with Decorative Paneling and Hangar Arm Removed

Ridgeline Engineering Company 3 April 2019 Portland Aerial Tram Body Panel Dislocation Incident

On December 4 th , 2018 one of these decorative panels came free from the cabin and fell to the ground. Figure 4 below shows Cabin #2, the one involved in the incident, with the panel that fell removed.

Figure 4 - Cabin #2 With Panel Removed

Ridgeline Engineering Company 4 April 2019 Portland Aerial Tram Body Panel Dislocation Incident

3. ANALYSIS OF FAILURE

For one of the decorative panels to fall from the cabin the panel latch and tether system must fail. Each panel is held in place by multiple spring latches and two tethers, therefore a panel cannot disengage unless both the spring latches and the tethers fail at the same time. The panel in question includes 8 latches distributed around the perimeter of the panel shown in Figure 5 below. The latches that failed during the incident are removed from the panel and can be seen in Figure 6.

Figure 5 - Panel Removed from Cabin; Latch Locations Circled in Red

Figure 6 – Spring Latches Removed from Panel

Ridgeline Engineering Company 5 April 2019 Portland Aerial Tram Body Panel Dislocation Incident

While it is impossible to conclusively say why the panel was pulled from the cabin, based on the information that was observed during our visit, it seems that the most likely reason the panel came loose was from lack of stiffness of the panel. Wind traveling over a panel of this shape produces an uplift force. This uplift force causes the panel to flex upward which in turn causes the sides of the panel to pull inward. As the sides move inward the contact area between the latches and their attachment to the cabin goes down until the point where they completely lose contact and the panel is pulled from the cabin. A schematic illustration of this situation can be seen below in Figure 7.

Figure 7 - Schematic of Panel Latch Failure; Clouded Area Shows where Latches Lost Contact with Cabin

Ridgeline Engineering Company 6 April 2019 Portland Aerial Tram Body Panel Dislocation Incident

The incident report provided by Doppelmayr, the tram operator, states that the wind was gusting as high as 38 mph at the time of failure. Considering this wind speed, and the formulas for calculating wind pressure in ASCE7-10, the estimated uplift force from the wind at the time of the incident was just under 500 pounds. Applying this force to our 3D stress analysis model of the panel produced the following result:

Figure 8 – Diagram of Deflected Roof Panel Under Load; Original Panel Shape in Gray, Deflected Shape in Colored Plot, Deformations Exaggerated for Clarity

The cabin manufacturer provided a tether system to catch the panels in the event that they came loose from the cabin. The size of the hardware used in the system indicates that the tether was likely designed to prevent the panel from falling to the ground if a technician were to accidentally drop it during maintenance. The design of the hardware was inadequate to restrain the wind forces on the panel during the incident. Images of the tether system, including the carabiner that failed can be seen in the following figures.

Figure 9 – Original Caribiner (Left); Recovered Portion of Broken Carabiner (Right)

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Figure 10 – Original Steel Cable Tether with Locking Chain Link (Above); Temporary Tether (Below)

4. DOCUMENT REVIEW AND MAINTENANCE PROCEDURES

Gangloff, the cabin manufacturer, did not provide any maintenance procedures or inspection criteria for the tram cabins. As such, the operations and maintenance documents do not provide any guidance for PBOT or Doppelmayr, the tram operator, to follow. Currently, there is no documentation in place that specifically details when the panel attachment to the cabin was last inspected. It should be noted, however, that other maintenance procedures that are currently in place require the removal and reinstallation of these panels at least twice per month. The frequency of the panels being indirectly inspected through other maintenance activities points towards a design failure not inadequate maintenance. Since the incident occurred, Doppelmayr has created a new maintenance program, 1M34, to address the future inspection of the panels, latches and updated tether system.

5. REMEDIATION

Since the tram opened in 2006 it has completed over 600,000 trips. During this time, the panel latch and tether system has malfunctioned twice and had one complete failure during the incident on December 4th , 2018. During both malfunction events a panel came loose from the cabin but was prevented from falling by the tether. Conversations with the Tram staff indicate that after each of the malfunctions the panel latches were revised in an attempt to prevent future failures. During the most recent malfunction, which occurred in January of 2014, the size of the restraint latches was increased, and a second tether was added to each panel. Ridgeline recommends that both the panel latch and safety tether components of the system are revised to prevent a future incident of this nature.

Ridgeline Engineering Company 8 April 2019 Portland Aerial Tram Body Panel Dislocation Incident

Panel Latch System The recent incident has proven that the spring latch system that was originally designed by the cabin manufacturer Gangloff is inadequate to resist the wind forces on the cabin. Ridgeline recommends that the roof panels are mechanically attached to the cabin using bolts which restrain movement in all directions rather than in a single direction like the spring latches in the current design.

Safety Tether System At the close of operations on the day of the event, tram maintenance staff installed a new interim safety tether system consisting of two tethers per panel, fabricated from rock climbing hardware, to all removable panels on both tram cabins. The strength of this system, 22 kN MBS lanyard and 7 kN MBS carabiner, is far superior to that of the failed tether. Ridgeline recommends that the permanent tether system includes both a revised lanyard system as well as stronger anchor points.

6. INTERIM OPERATIONS

Given the timeframe required to fabricate and install the new components discussed in this report, Ridgeline recommends making the following changes to system operations with respect to wind:

Current Condition of Tram: • Tram should not be operated with cabin roof air vents open above sustained wind speeds of 20 mph. • Tram should not be operated with cabin air vents open or closed with sustained wind speeds above 30 mph.

Operations After Ridgeline Designed Safety Tether is Installed: • Tram should not be operated with cabin roof air vents open above sustained wind speeds of 35 mph. • Tram should not be operated in wind conditions that exceed those described in the Operations Manual.

Note: Tether will restrain the full force of a panel detaching from the cabin, however, the current latches may not be adequate to hold the panel in place, especially if one or more of the roof panels are removed from the tram. Operator to monitor the wind and any movement of the panels carefully in this condition.

Operations After Ridgeline Designed Safety Tether & Panel Latch System are Installed: • Resume normal operations as described in the Operations Manual.

Ridgeline recommends fabricating and installing the new safety tether system as soon as possible. Wind conditions are unpredictable and can change drastically during the time it takes to complete a trip. Conditions should be monitored closely until the new safety tether system is in place.

7. CONCLUSION

A new permanent panel anchorage and safety tether system has been designed by Ridgeline Engineering Company and is expected to be installed before the end of Summer 2019. This new system is designed to meet the wind requirements of IBC 2015, as referenced by ANSI B77.1 – 2017, using a basic wind speed of 115 MPH which is in excess of the maximum operation wind speed per the Operations Manual. Once

Ridgeline Engineering Company 9 April 2019 Portland Aerial Tram Body Panel Dislocation Incident the new system is implemented normal operations can be resumed as described in the Operations Manual.

Ridgeline Engineering Company 10 April 2019 Portland Aerial Tram Body Panel Dislocation Incident

APPENDIX A ADDITIONAL PHOTOS

Ridgeline Engineering Company April 2019 Photos of Failed Latches and Lanyard System

Appendix A - Page 1 of 33 Photos of Panel That Fell From Cabin

Appendix A - Page 2 of 33 Photos of Panel That Fell From Cabin

Appendix A - Page 3 of 33 Photos of Panel That Fell From Cabin

Appendix A - Page 4 of 33 Photos of Panel That Fell From Cabin

Appendix A - Page 5 of 33 Photos of Panel That Fell From Cabin

Appendix A - Page 6 of 33 Photos of Panel That Fell From Cabin

Appendix A - Page 7 of 33 Photos of Panel That Fell From Cabin

Appendix A - Page 8 of 33 Photos of Panel That Fell From Cabin

Appendix A - Page 9 of 33 Photos of Panel That Fell From Cabin

Appendix A - Page 10 of 33 Photos of Panel That Fell From Cabin

Appendix A - Page 11 of 33 Photos of Panel That Fell From Cabin

Appendix A - Page 12 of 33 Photos of Air Vent Panel - Panel Stayed Attached During Event

Appendix A - Page 13 of 33 Photos of Air Vent Panel - Panel Stayed Attached During Event

Appendix A - Page 14 of 33 Photo of Air Vent Panel - Panel Stayed Attached During Event Photos of Panel That Fell From Cabin

Appendix A - Page 15 of 33 Photos of Panel That Fell From Cabin

Appendix A - Page 16 of 33 Photos of Air Vent Panel - Panel Stayed Attached During Event

Photo of Top of Cabin with Panel Removed

Appendix A - Page 17 of 33 Photo of Top of Cabin with Panels Removed

Appendix A - Page 18 of 33 Photo of Top of Cabin with Panels Removed

Appendix A - Page 19 of 33 Photo of Top of Cabin with Panels Removed

Appendix A - Page 20 of 33 Photo of Top of Cabin with Panels Removed

Appendix A - Page 21 of 33 Photo of Top of Cabin with Panels Removed

Appendix A - Page 22 of 33 Photo of Top of Cabin with Panels Removed

Appendix A - Page 23 of 33 Photo of Top of Cabin with Panels Removed

Appendix A - Page 24 of 33 Photo of Top of Cabin with Panels Removed

Appendix A - Page 25 of 33 Photo of Top of Cabin with Panels Removed

Appendix A - Page 26 of 33 Photo of Top of Cabin with Panels Removed

Photos of Cabin

Appendix A - Page 27 of 33 Photos of Cabin

Appendix A - Page 28 of 33 Photos of Cabin

Appendix A - Page 29 of 33 Photos of Cabin

Appendix A - Page 30 of 33 Photos of Cabin

Appendix A - Page 31 of 33 Photos of Cabin

Appendix A - Page 32 of 33 Photos of Cabin

Appendix A - Page 33 of 33 Portland Aerial Tram Body Panel Dislocation Incident

APPENDIX B DOPPELMAYR INCIDENT REPORT

Ridgeline Engineering Company April 2019

Incident Report

Date:______12-4-2018- Time:______11:52AM Report Taken By:______Mark Leslie______Incident #____

Exact Location:______Pedestrian Bridge ______

Guest Name:______Rose Sprauer Phone #:______(5003)-758-9211______

Address:[email protected] ______

Weather:______Footwear:______Weatsunny/windy sneakers her:______sunny/windy

OSHU Public Safety Notified: Yes No OHSU Risk Notified: Yes No

Personnel Involved:______Mark Leslie, Ian Glazebrook, Stephaine Diouf ______

On Duty: Supervisor:______Mark Leslie GM Notified:______Yes

Photos Taken: Yes No Photographer:______Mark Leslie ______

Property Damage: Yes No (If Yes Describe Below) ______Cabin 2 uphill large roof pannel ______

Injuries: Yes No (If Yes Describe Below) Fatality: Yes No (If Yes Describe Below) ______Small bump on right side of females head. ______

Incident Details:______At 11:52 AM, Cabin 2 called on the radio to come up______to the dock from attendant Stephaine ______Diouf. Arriving onto the dock, we had noticed that the large pannel on top of ______Cabin 2 was off. Looking up at ______the tower, I noticed it just below the Pedestrian Bridge. Went up to look and ______saw Miss Sprauner sitting on the ______stairs. then I proceeded to ask if she needed medical attention and she replied______that she didn't need it. After ______I relocated the pannel to the inside of the tower. An inspection was done to ______make sure that the remaing ______panels were secure in there positions and resumes operations around 12:05.______(For Additional Space See Page 2)

Could Incident Have Prevented: Yes NO (If Yes Describe Below) ______

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Incident Report

Witnesses: (Collect Full Name and Contact Information) Incident #:______

Additional Comments:______At the time of the incident, another pedestrian had called paramedics.______Ian Glazebrook stayed ______with Miss Sprauer untill medics showed up. She refused help and walked away______freely under her own power. ______The cabin attendant Stephaine stated he heard one "whoosh" sound and people______in the cabin said something ______had fallen off. The tram was travelind downhill over the tower at 7 m/s (full ______speed over tower). There has ______been a steady east wind averaging 25 mph with gusts as high as 38 mph according______to our anemometer. ______It is concluded that the carabiner had failed. ______

Diagram:

Investigated By:______GM Initials:______

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